A display device forms an image in the air by combining an optical element which transmits or reflects incident light and a retroreflective element which retroreflects incident light. For example, an optical device which comprises a first retroreflective member and a second retroreflective member is known. The first retroreflective member reflects the light flux reflected on a reflective member (partial reflective member) having a transmittance of 70% and a reflectance of 30% to the partial reflective member. The second retroreflective member reflects the light flux having passed through the partial reflective member to the partial reflective member. When the reflective surface of the retroreflective element has a region which does not exhibit a retroreflective property, the light having entered the region does not contribute to formation of an image. As a result, the image in the air may be discontinuous.